Sync Sync Sync Sync Sync hr hr hr hr hr o o o o o or or or or or que que que que que Producing Recei Recei Recei Recei Recei er er er er er When driving Synchro Torque Recievers power is pulled from
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Sync Sync Sync Sync Sync hr hr hr hr hr o o o o o or or or or or que que que que que Producing Recei Recei Recei Recei Recei er er er er er When driving Synchro Torque Recievers power is pulled from

AND 2 The Power Amplifiers 3 wire synchro outputs S1 S2 and S3 stator coils Torque recievers provide torque as a result of the interaction of the two magnetic fields introduced through these coils within the torque reciever itself The torque recie

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Sync Sync Sync Sync Sync hr hr hr hr hr o o o o o or or or or or que que que que que Producing Recei Recei Recei Recei Recei er er er er er When driving Synchro Torque Recievers power is pulled from




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Presentation on theme: "Sync Sync Sync Sync Sync hr hr hr hr hr o o o o o or or or or or que que que que que Producing Recei Recei Recei Recei Recei er er er er er When driving Synchro Torque Recievers power is pulled from"— Presentation transcript:


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Sync Sync Sync Sync Sync hr hr hr hr hr o o o o o or or or or or que que que que que (Producing) Recei Recei Recei Recei Recei er er er er er When driving Synchro Torque Recievers, power is pulled from and against the 2 following sources: 1) The Torque Reciever itself: Via 26 or 115VAC on its rotor coil, R1 & R2 rotor coil. ----------- AND ----------- 2) The Power Amplifiers 3 wire synchro outputs, S1, S2 and S3 stator coils. Torque recievers provide torque as a result of the interaction of the two magnetic fields introduced through these coils within the torque reciever

itself. The torque reciever is considered an active load in that it works against the opposing stator coil inputs, thereby loading them to produce the torque required of its shaft. Torque is produced whenever the torque recievers shaft angle differs from the angle dictated by its 3 wire stator input. The angular difference is reflected as a voltage gradient that develops circulating currents in the stators, working against the rotors magnetic field. These opposing stator currents provide the magnetomotive force against the rotors magnetic field, to move the rotor shaft. Theoretically, when

the shaft angle is positioned exactly to the angle dictated by its 3 wire synchro input (respective of the phasing of its rotor input); the load impedence is infinite, the shaft is nulled and the load is null. In practice however, the amplifiers outputs must still accomodate the load incurred by virtue of both the voltage and phase differen- tials existing between the amplifier outputs and the actual charac- teristics of the torque recievers imperfect stator coils. These differential effects are significant, and must be considered when specifiing appropriate amplifiers for a given

application. Dr Dr Dr Dr Dr ving Sync ving Sync ving Sync ving Sync ving Sync hr hr hr hr hr o o o o o or or or or or que que que que que (Pr oducing) Recei Recei Recei Recei Recei er er er er er When driving torque recievers: the amplifier must be able to handle both: the peak transient power required to be able to drive the torque reciever to a null (close the loop), in addition to being able to supply enough steady state, continuous power to maintain the torque reciever at null, accomodating the circulating currents at the null resulting from phase shift and voltage differentials in the

driven synchro, the amplifier, and the D-S converter or other synchro driving the amp. When driving a Torque Receiver, like driving a servo, we are constantly attempting to null the circuit to achieve any desired position, to null a 3 wire synchro consider the voltage required at null in a 3 wire synchro format as: sine(120 )(Vm) Vm = voltage magnitude Vm for a 115V/90V L-L synchro: (.866)(90V.L-L) = 78 V. L-L Vm for a 26V/11.8V L-L synchro: (.866)(11.8) = 10.2 V. L-L This Vm (Voltage magnitude) is the voltage that will be measured with two stator legs shorted accross the remaining winding.

See the following illustration "Zss": Fig. Zss, Driving Torque Receiver Loads he po he po he po he po he po er amplif er amplif er amplif er amplif er amplif ier's Zss (output impedence) m ier's Zss (output impedence) m ier's Zss (output impedence) m ier's Zss (output impedence) m ier's Zss (output impedence) m ust be lo ust be lo ust be lo ust be lo ust be lo enough to dr enough to dr enough to dr enough to dr enough to dr e the combined Zss of all the e the combined Zss of all the e the combined Zss of all the e the combined Zss of all the e the combined Zss of all the or or or or or que r

que r que r que r que r ecei ecei ecei ecei ecei er er er er er being dr being dr being dr being dr being dr en, en, en, en, en, (plus the Zso of all the CT's and CDX's being driven off the same load (less if these are tuned)), to accomodate the peak transient power required to be able to drive the torque reciever/'s shaft to a null (close the loop). Ad Ad Ad Ad Ad ditionall ditionall ditionall ditionall ditionall , the Synchro Amplifier ust be a ust be a ust be a ust be a ust be a le to pr le to pr le to pr le to pr le to pr vide vide vide vide vide enough contin enough contin enough contin

enough contin enough contin uous po uous po uous po uous po uous po er to accomoda er to accomoda er to accomoda er to accomoda er to accomoda te the cir te the cir te the cir te the cir te the cir cula cula cula cula cula ting ting ting ting ting cur cur cur cur cur ents r ents r ents r ents r ents r especti especti especti especti especti e of the phase shift and v e of the phase shift and v e of the phase shift and v e of the phase shift and v e of the phase shift and v olta olta olta olta olta e missma e missma e missma e missma e missma tc tc tc tc tc (Vmm), (Vmm), (Vmm), (Vmm), (Vmm), r

r r r r equir equir equir equir equir ed just to maintain a n ed just to maintain a n ed just to maintain a n ed just to maintain a n ed just to maintain a n ull. ull. ull. ull. ull. Calcula Calcula Calcula Calcula Calcula ting Load Impedances Requir ting Load Impedances Requir ting Load Impedances Requir ting Load Impedances Requir ting Load Impedances Requir ed to Maintain a Null ed to Maintain a Null ed to Maintain a Null ed to Maintain a Null ed to Maintain a Null (To maintain desired position, minimum continuous current flow) The criteria used to determine the effective load impedence at

null, or effectively how much power will be required just to maintain a constant position, we must consider the voltage mismatch and phase shift respective of the components used in the system. 1) 1) 1) 1) 1) Line to line olta olta olta olta olta e e e e e difference between the amplifiers outputs and the torque recievers stator, (differential voltage, misma misma misma misma misma tc tc tc tc tc or magnitude error, = Vmm). ---------------- AND AND AND AND AND ---------------------- 2) 2) 2) 2) 2) Phase Shift: Line to line phase-shift dif phase-shift dif phase-shift dif phase-shift dif

phase-shift dif er er er er er ential ential ential ential ential between the amplifiers outputs and the torque recievers stator. The active load calculations derived by these two variable differen- tials may be referred to as the null wattage or the VA @ null required, the power exhibited as circulating currents flowing just to maintain a null (any constant position), which is lost wattage above and in addition to the VA required of the amplifier to produce any torque. _____________________________________________________ _____________________________________________________

_____________________________________________________ _____________________________________________________ _____________________________________________________ Calcula Calcula Calcula Calcula Calcula ting line to line "V ting line to line "V ting line to line "V ting line to line "V ting line to line "V olta olta olta olta olta e Missma e Missma e Missma e Missma e Missma tc tc tc tc tc h" @ n h" @ n h" @ n h" @ n h" @ n ull ull ull ull ull A) When driven from a digital to synchro converter, that part's "Transformation Ratio Accuracy" is the criteria required, it is not usually specified on

D-S converters which normally only specify accuracy with respect to the ratio accuracy. For standard CCC D-S APPLICATION NOTE #G-SA1 DRIVING SYNCHRO LOADS With Synchro Amplifiers and Converters page 1of 4 c CCC 1998 c CCC 1998
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converters this is typically +/-2%, and may be trimmed to +/-1% on request. It is benificial to source both the Amp and the converters from the same source and request they be matched interchangeably, this will minimize the voltage missmatch. B) The Scale factor accuracy specified of a good Reference Powered Synchro Amplifier is +/-1%. On conventional DC

powered (non-pulsating) amplifiers this absolute scale factor accuracy may be as much as +/- 8%. The Transformation Ratio (Input to Output) tolerance of most synchros is typically +/-2%: *Amplifier Scale Factor accuracy, +/-1.% Sync hr o ansf or ma tion Ra tio: +/- 2.% Total Voltage missmatch: +/-3.%. * Amplifier Reference Powered type with D-S converters trimmed to match where any combined represents +/-1%. +/-3.0% voltage differential (or missmatch) can be used for nominal calculations, with 1 synchro TR and any of CCC's Reference Powered Synchro Amplifiers. When driving a Torque Receiver,

like driving a servo, we are constantly attempting to null the circuit to achieve any desired position, to null a 3 wire synchro consider the voltage required at null in a 3 wire synchro format as: sine(120 )(V.L-L) for a 115V/90V 115V/90V 115V/90V 115V/90V 115V/90V L-L sync sync sync sync sync hr hr hr hr hr : (.866)(90V.L-L) = 78 = 78 = 78 = 78 = 78 . L-L . L-L . L-L . L-L . L-L for a 26V/11.8V 26V/11.8V 26V/11.8V 26V/11.8V 26V/11.8V L-L sync sync sync sync sync hr hr hr hr hr : (.866)(11.8) = 10.2 10.2 10.2 10.2 10.2 . L-L . L-L . L-L . L-L . L-L When driving a synchro Torque Reciever using

115V 115V 115V 115V 115V C C C C C reference and 90 V.L-L stators, anticipate this 3.% in synchro system tolerances, will yield a olta olta olta olta olta e Missma e Missma e Missma e Missma e Missma tc tc tc tc tc of 2.34V. 78V.L-L (.03 System Tolerance) = = = = = 2.34V 2.34V 2.34V 2.34V 2.34V .L-L = .L-L = .L-L = .L-L = .L-L = Vmm Vmm Vmm Vmm Vmm The following figure further illustrates the power required at null (actually to satisfy the circulating currents that will be flowing) attributed to the voltage differential (magnitude error, or component missmatch) in the synchro system driving a

T.R.. ig . Vmm, v olta e misma tc h cur ents @ n ull Take the magnitude of the voltage missmatcth (V1 -V2) over the total impedence of the circuit (output impedence of the transmitter or amplifier (ZSS = Z ) - the impedence of the Receiver (ZSS = ). This current times the nominal voltage (78V. for 115/90V systems) represents the power flowing at null in VA or watts, just to satisfy the voltage mismatch.. If multiple synchro's are being driven, only the impedence of the receivers side needs to be changed, calculate like adding resistors in parallel: = ZSS = Z olta olta olta olta olta e Misma e

Misma e Misma e Misma e Misma tc tc tc tc tc h and h and h and h and h and Amplif Amplif Amplif Amplif Amplif ier Headr ier Headr ier Headr ier Headr ier Headr oom: oom: oom: oom: oom: The voltage mismatch must also be considered with respect to the negative potential of the missmatch verses the amplifiers voltage envelope, to insure there is sufficient headroom such that the negative flowing currents do not try to backfeed or buck the amplifier outputs, possibly causing damage to the amplifier. This is explained in greater detail in the following section regarding large phase shifts, and

includes both the tolerance of different synchro amplifiers, and the means to increase the headroom and ZSS in the system, and at the synchro amplifier itself. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ Calcula Calcula Calcula Calcula Calcula ting line to line phase-shift dif ting line to line phase-shift dif ting line to line phase-shift dif ting line to line

phase-shift dif ting line to line phase-shift dif er er er er er ential @ n ential @ n ential @ n ential @ n ential @ n ull: ull: ull: ull: ull: (between the amplifiers outputs and the torque recievers stators) When reference powered amplifiers are used, the 3 wire synchro outputs are in phase with the reference input, the phase shift specified of the Torque Reciever being driven provides the line to line phase-shift differential. Theoretically, when driving only one synchro this effect can be minimized by adding a phase shift compensation RC (Resistor Capacitor Network) in series with the

rotor input of and at the source of each synchro being driven, on many preinstalled synchro applications this luxury is usually not a practical expectation. Alternatively, adding a large capacitor in series with the Reference input of the Synchro Amplifier can be considered, but this also requires a RC phase lead/lag network be added to the synchro or D-S converter driving the amplifier itself. Lar Lar Lar Lar Lar e Phase Shift Ef e Phase Shift Ef e Phase Shift Ef e Phase Shift Ef e Phase Shift Ef ects: ects: ects: ects: ects: Most installations specify power sufficient to accomodate the

increased load required to maintain a null, respective of both the phase shift and voltage mismatch differentials required of the synchro's employed, but the voltage tolerance especially with respect to the phase shift should be calculated to insure there is enough voltage mismatch headroom, that the negative flowing currents do not try to backfeed or buck the amplifier outputs, possibly causing damage to the amplifier. Phase shift differentials can be significant, example: a typical 15TRX6a has a 20 degree phase shift, a 23TR6 is 9.1 degrees, also consider the phase shift tolerence between

like manufactured synchros is approx. +/-20% of that nominally specified. This is further complicated when driving multiples of differing synchros off of one common amplifier. When Reference Powered Synchro Amplifiers are used to drive synchro Torque Receivers having large phase shifts, the phase shift limits the peak voltages available from the pulsating power supplies, this is because the pulsating power supplies' peak voltages are full-wave rectified, and in phase with, the reference (power) APPLICATION NOTE #G-SA1 DRIVING SYNCHRO LOADS With Synchro Amplifiers and Converters page 2of 4 c

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input. The peak magnitude of the voltage seen as phase shifted away from the reference is less. This makes the amplifiers effective output voltage envelope smaller, limiting or reducing the peak amplitude available on the outputs with respect to the synchro's desired phasing. The more undesireable effect (from phase shift) is when the synchro stator signals being driven by the amp., exhibit a higher voltage (by virtue of the induced rotor voltage coupling working against the stators) than the peak voltages being produced by the amplifier. This results in a ne ne ne ne

ne ti ti ti ti ti e v e v e v e v e v olta olta olta olta olta e misma e misma e misma e misma e misma tc tc tc tc tc which, if significant enough will tr will tr will tr will tr will tr y to bac y to bac y to bac y to bac y to bac kf kf kf kf kf eed or b eed or b eed or b eed or b eed or b uc uc uc uc uc k the sync k the sync k the sync k the sync k the sync hr hr hr hr hr amplif amplif amplif amplif amplif ier ier ier ier ier s output sta s output sta s output sta s output sta s output sta es es es es es Calcula Calcula Calcula Calcula Calcula tions f tions f tions f tions f tions f or the

ef or the ef or the ef or the ef or the ef ects of Phase Shift on Sync ects of Phase Shift on Sync ects of Phase Shift on Sync ects of Phase Shift on Sync ects of Phase Shift on Sync hr hr hr hr hr o o o o o Amp. Amp. Amp. Amp. Amp. To calculate the circulating currents that will be flowing at null attributed to phase-shift, first calculate the Voltage magnitude error, (or the voltage offset) incurred by the phaseshift, over the total impedence of the circuit (output impedence of the transmitter or amplifier ZSS = Z ) + the impedence of the Receiver (ZSS = Z ): Sine (phase shift in de ees)

(Vm) = Vme Z + Z To calculate the power that will be lost to phase shift to simply maintain a null: I (Vm) = VA Where Vm = Voltage magnitude used to Drive Synchro, Vm = for 115/90 Systems use 78V, Vm = for 26/11.8V Systems use 10.2V Vme = Voltage Magnitude Error, this voltage will be present on the driven synchro's leads, fighting against the power amplifiers outputs, at the zero-crossings of the reference input sine wave, when the reference input is providing no instantaneous power, and likewise, the dynamic pulsating supply has no instantaneous power to transfer; at the instant of these

(reference/power input) zero crossings; the amplifier is essentially driving 0V, 0 current (less mismatch), while the driven synchro inductively applies to the same signal lines its phase shifted voltage potentials. The difference between the voltage seen from the driven synchro, at the zero-crossings of the pulsating supply; must fit into the headroom tolerated by the amp. If the phase shift line to line voltage plus the mismatch exceeds the voltage missmatch headroom tolerated by the amp.: the phase shift must be compensated for, or external resistors must be used, on the stator lines to

increase the headroom, or both. Sync Sync Sync Sync Sync hr hr hr hr hr o o o o o Amplif Amplif Amplif Amplif Amplif ier Headr ier Headr ier Headr ier Headr ier Headr oom: oom: oom: oom: oom: The negative voltage missmatch that CCC's Reference Powered Synchro Amp's. are designed to tolerate for 115V/90V. units are as follows, (this is your headroom tolerance): 25 VA unit: 6.7 Volts/leg, (2) = 13.4 Volts across winding 50 VA unit: 2.45 Volts/leg, (2) = 4.9 Volts across winding 100 VA unit: 1.73 Volts/leg, (2) = 3.46 Volts across winding ec ec ec ec ec hniques used to incr hniques used to incr

hniques used to incr hniques used to incr hniques used to incr ease the Sync ease the Sync ease the Sync ease the Sync ease the Sync hr hr hr hr hr o o o o o Amplif Amplif Amplif Amplif Amplif ier Headr ier Headr ier Headr ier Headr ier Headr oom: oom: oom: oom: oom: 1) 1) 1) 1) 1) Ad Ad Ad Ad Ad ding Load Balancing Resistor ding Load Balancing Resistor ding Load Balancing Resistor ding Load Balancing Resistor ding Load Balancing Resistor (illustrated in figure LBR) To increase the amount of negative voltage mismatch tolerated by the amp. without shutting down the outputs, the user can add

large (10 - 20) watt resistors in series with the amplifiers synchro outputs representing upto 2/3rd's of the synchro load being driven (repre- sented as the ZSS "Stator impedence rotor shorted", specified for the synchro (or synchro's) being driven in each leg. The added resistors will effect the current flow through the synchro, the synchro signals however will still read 90 V.L-L. The higher the total line impedences, the lower the current flow at null. Though this will certainly help minimize the voltage at null, and lower the current flow. There may be a slight reduction in peak torque

available on the synchro's output shaft (when driving very large shaft loads). hen dr hen dr hen dr hen dr hen dr ving m ving m ving m ving m ving m ultiple sync ultiple sync ultiple sync ultiple sync ultiple sync hr hr hr hr hr o loads, o loads, o loads, o loads, o loads, load load load load load shar shar shar shar shar ing ef ing ef ing ef ing ef ing ef ects' can and will minimiz ects' can and will minimiz ects' can and will minimiz ects' can and will minimiz ects' can and will minimiz e loss of tor e loss of tor e loss of tor e loss of tor e loss of tor que que que que que Occasionally,

when driving several different Torque Receivers with large shaft loads, compromise may be required, and the user may have to try a couple of different load balancing resistors, or phase shift capacitors to the amp's. reference input to optimize driving the loads. When driving multiple synchro Torque Recievers, the phase shift should be apportioned respective of the ZSS rating of each synchro verses its phase shift, the larger that synchros load (the lower its Fig. PS-(Vme), Phase Shift Voltage Magnitude Error Phase Shift Measurements, and effect: Load Balancing Resistor s & Phase Shift ad ded

to Sync hr o Amp. = I APPLICATION NOTE #G-SA1 DRIVING SYNCHRO LOADS With Synchro Amplifiers and Converters page 3of 4 c CCC 1998 c CCC 1998
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ZSS impedence), the more its effect of phase shift will burden the system. Ad Ad Ad Ad Ad ding Lead/La ding Lead/La ding Lead/La ding Lead/La ding Lead/La g RC netw g RC netw g RC netw g RC netw g RC netw or or or or or ks f ks f ks f ks f ks f or phase shift compensa or phase shift compensa or phase shift compensa or phase shift compensa or phase shift compensa tion tion tion tion tion If the phase shift is large, the user may add (or

order with internal) a phase shift lead/lag RC (resistor/capacitor) network on the D-S converters reference input lines, and, use a large capacitor on the reference input of the synchro amplifier to compensate for the average phase shift of the load driven. If a 115V, 60 Hz. synchro system is being used, start with a 10 Uf. 400V cap. in series with RH on the synchro amp., simply measure phase shift between S1-S3 out verses the RH-RL in , when loaded, on a dual-trace scope. The formula used to calculate the phase shift for the D-S are as follows: tan = R Where = the phase shift in degrees. XC =

1 2 fc Where: f = frequency, c = capacitance Phase Shift Lead/La g RC placement on D-S Con er ter Fig. PSL/L The input impedence of the reference input specified for the D-S converter is required as part of "R" resistor component (see Data Sheets). CCC con er ter s ar e a aila le with inter nal phase shift. Control T ransformer CT's and CDX type Synchro's CT's are relatively high impedence rotary transformers that provide a single phase AC rotor output representing the sine of the differ- ence between the absolute shaft angle of it's rotor and it's 3 wire stator (command) inputs. CT's are

typically coupled directly on the apparatus being controlled, providing instantaneous position feedback and control, it's output is typically amplified to drive a servo motor direct, thus the motor automatically nulls it's shaft to the command angle dictated by the CT's 3 wire input. CT's' are typically driven from a CX (control transmitter) or CDX (control differential transmitters). CDX's (control differential transformers) have a 3 wire primary input, a physical rotor shaft angle input, and a 3 wire secondary output used to drive CT's other CDX's or even TR (Torque Receiver) inputs. The CDX

output is a 3 wire synchro format representing the angular difference between the absolute shaft angle of it's rotor input and the shaft angle command determined by it's 3 wire synchro input. Because the CDX is used to drive other synchro's, it's load must be added to the loads required of all the synchro's connected to it's outputs, to determine the full magnitude of the load burden that will be required of it's inputs. CDX's are typically driven from a CX (control transmitter) or another CDX, the are used as active offsets in a synchro chain to bias their synchro inputs by the shaft angle of

their rotor.. Dr Dr Dr Dr Dr ving CT's and CDX's ving CT's and CDX's ving CT's and CDX's ving CT's and CDX's ving CT's and CDX's When driving CT's or CDX's the amplifier must be able to supply enough steady state, continuous power to drive the Zso of the load. Fig. Zss, Driving Control Transformer (CT) and CDX Loads er F er F er F er F er F actor Cor actor Cor actor Cor actor Cor actor Cor ection b ection b ection b ection b ection b y y y y y uning CT's and CDX's uning CT's and CDX's uning CT's and CDX's uning CT's and CDX's uning CT's and CDX's Unlike the more resistive load requirements of

Torque Receivers; CT's and CDX's are primarily inductive loads, whereby power factor correction can be achieved to reduce the reactive component by simply tuning the loads. CT's and CDX's may be tuned by adding good grade, unpolarized, poly-type, high voltage tuning capacitors in a delta configuration, in parallel with the stator inputs (see illustration, use 400V. min. capacitors for 90 V. L-L signals). The use tuning capacitors can reduce the load burden to the synchro, or even a whole chain of synchro's by as much as 50%. Fig. TC, Adding Tuning Capacitors for CT Type Loads APPLICATION NOTE

#G-SA1 DRIVING SYNCHRO LOADS With Synchro Amplifiers and Converters page 4of 4 c CCC 1998 c CCC 1998 c CCC 1998 4 pi f